1. Field of the Invention
The present invention relates to an endoscope system that is constituted of an electronic endoscope, a processor device and a light source device, and a method for inspecting the electronic endoscope.
2. Description Related to the Prior Art
An endoscope system is constituted of an electronic endoscope, a processor device and a light source device. The electronic endoscope has a solid-state image sensor at its distal portion for capturing an image of a human body cavity to output an image signal. The processor device receives the image signal from the solid-state image sensor and produces an image to display it on a monitor. The light source device supplies the electronic endoscope with light. Inside the electronic endoscope, a light guide extends. The light from the light source device is led into the distal portion of the electronic endoscope through the light guide, and is incident on the human body cavity from lighting windows provided in the distal portion.
The light guide consists of a plurality of optical fibers tied in a bundle and a binder such as a tape for wrapping the bundle. Since the optical fibers become rigid with a lapse of time, the optical fibers gradually deteriorate and finally snap due to stress applied in using the electronic endoscope. Accordingly, JPA No. 2006-55664 discloses to cover the optical fibers with a flexible tube which has holes formed at regular intervals, for the purpose of preventing a break of the optical fibers. Such a flexible tube, however, cannot always prevent the break because the optical fibers necessarily deteriorate with time.
The break of the optical fibers in the light guide causes reduction in the amount of light exiting from the light guide in accordance with the number of broken optical fibers. Thus, JPA No. 2002-58640 discloses to provide an aperture stop between an incident end of the light guide and a light source in order to keep the amount of exit light constant. The amount of light exiting from the light guide is measured based on an image signal from the solid-state image sensor. The aperture stop is actuated on the basis of a measurement result to control the amount of exit light. Adjustment by the aperture stop, however, is insufficient in a case where a predetermined number or more of optical fibers have already snapped. In this case, a shortage of light exiting from the light guide darkens the image, so that the light guide needs repairing.
A conventional endoscope system cannot detect the break of the optical fibers in the light guide. Therefore, a user cannot grasp appropriate timing of repairing the light guide, and hence it may happen that a doctor has found a shortage of exit light after inserting the electronic endoscope into a patient's body, and the electronic endoscope has to be pulled out and replaced. To prevent such an event, it is conceivable to repair the light guide early on before the electronic endoscope is short of the exit light. However, repair at an early stage causes increase in costs.